Researchers may have found a method to preserve ovarian function in patients
undergoing radiotherapy and possibly chemotherapy.
Dr Yutaka Morita (Vincent centre for reproductive biology, Massachusetts general
hospital/Harvard medical school, Boston, US) and colleagues investigated the
use of sphingosine-1-phosphate (S1P) in mice. S1P inhibits apoptosis which,
they say, has been identified as a mechanism responsible for oocyte loss.
The researchers demonstrated that S1P reduced oocyte death and then investigated
the effect of S1P in vivo in mice exposed to ionising radiation. In control
mice, there was nearly complete destruction of the ovaries two weeks after irradiation.
However, in mice treated with S1P two hours before irradiation, there was a
significant and dose-dependent preservation of the ovaries, they say. The protective
effect was apparent by both quantitative assessment of oocyte counts and qualitative
assessment of changes in ovarian tissue mass.
To examine oocyte viability, the researchers collected irradiated oocytes from
control mice and mice treated with S1P and fertilised them in vitro. Although
fertilisation rates did not differ between the two groups, embryonic development
was impaired in the oocytes that had not been protected by S1P. Oocytes protected
in vivo by S1P progressed normally to form high quality blastocytes. The researchers
comment: “These data support the idea that in vivo treatment with S1P effectively
preserves ovarian follicular dynamics and oocyte competency after irradiation.”
They add that in ongoing mating trials (unpublished), pregnancy rates had been
50 per cent in untreated irradiated mice and 100 per cent in irradiated mice
treated in vivo with S1P. They conclude that the research holds “great
promise” for preserving normal fertility in young girls and women of a
reproductive age treated for cancer (Nature Medicine 2000;6:1109).